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Brass vs. Bronze Fittings; galvanic & dielectric issues

Q. I'm installing a new thru hull and valve.
The valve is 1/2" thread, bronze.
The hose is 3/8".
I cannot find a bronze 1/2" thread, 3/8" barb, only 1/2 X 1/2 is available in bronze (smallest unit).
This is for an underwater fitting.
Is it acceptable to connect a brass hose barb to a bronze valve?
thanks

Steve walinski
boat owner - seymour, ct
December 24, 2022


A. Hi Steve. I don't know a good resolution, but apparently a brass hose barb is a bad idea →
Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey





Closely related historical posts, oldest first ...

Q. I work for a commercial HVAC company. We connect copper to steel using dielectric unions typically. I am wondering if using a brass and/or cast bronze fitting or valve can effectively prevent electrolysis from happening. For example, is it possible to screw a black malleable nipple into a threaded bronze ball, and then screw a copper male adapter into the other side without causing electrolysis? In this instance, the bronze ball valve would be used for a dielectric break. If situation in question can be done, where could I find some written documentation supporting that.

Zachary Wallace
Mechanical Contracting - Indianapolis, Indiana, USA
2005


A. 'Dielectric' means non-conductor, Zachary. You need a non-metallic section, which is usually done with some sort of plastic joint. If you connect a multimeter / V-O-M, you'll see essentially infinite resistance across a dielectric union, and essentially zero resistance across a regular union. If the bronze valve has union-type fittings, and these are dielectric unions, then it would work of course. If they are not dielectric it won't solve the problem.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey




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Q. DO I NEED TO USE DIELECTRIC FITTINGS BETWEEN COPPER AND BRASS CONNECTION

MARVI ENGAY
CONSTRUCTION - PHILIPPINES
November 22, 2008


A. Hi, Marvi. I'm no plumber, pipefitter or codes official ... but for typical homes I'd say "no" based on the fact that the two materials are close on the electrochemical potential scale, and the fact that a typical way to make the transition is with a brass fitting that is solderable on one end and threaded on the other.
But note that this does not apply to ships and boats, where galvanic corrosion can cause a catastrophe./P>

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey




Q. Hello Gentlemen,
I need your assistance to get these two questions off my back:
What chapter of the UPC or IPC allows the use of dielectric unions, devices or brass fittings for the proper transition when dissimilar metals?
And what chapter on the same codes prohibits the use of valves?

Marcos [last name deleted for privacy by Editor]
plumbing company - Phoenix, Arizona
May 1, 2015


A. Marcos,
Please see 2012 UPC 507.1; 605.16-605.17; 1210.1.3. Regarding the second question, perhaps you are referring to 2012 UPC 310.6.

blake kneedler
Blake Kneedler
Feather Hollow Eng. - Stockton, California


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